Properties of the Mg II absorption catalogue. Top: Redshift distribution of the Mg II absorption systems. The solid and gray histograms show the absorbers for the SDSS (DR1) and UVES (DR2) selections, respectively. Bottom: Rest-frame equivalent width $W_{\mathrm{r}}^{2796}$ distribution of the Mg II absorption systems. The dashed histogram shows the full sample of DR2 absorbers, while the solid and gray histograms represent the absorbers for the SDSS (DR1) and UVES (DR2) samples, respectively, over the same redshift interval 0.35 < z < 1.5. In order to compare the slope of the $W_{\mathrm{r}}^{2796}$ distribution to random QSO field, we show the REW distribution from Nestor et al. (2005) (solid line) at z = 1 (arbitrary normalisation). For $W_{\mathrm{r}}^{2796}>0.5$ Å, the 95% confidence interval of the REW slope is shown (tied to $W_{\mathrm{r}}^{2796}=1$ Å). The Mg II REW distribution in MEGAFLOW is not different than from random QSOs for strong Mg II absorptions. In both panels, the red (green) histogram represents the Mg II sample from Dutta et al. (2020), Lundgren et al. (2021), respectively.